Characteristics of a highly mismatched In/sub x/Ga/sub 1-x/As/AlGaAs (0/spl les/x/spl les/0.5) HEMT on a GaAs substrate

The performance of a highly mismatched In/sub x/Ga/sub 1-x/As/AlGaAs (0/spl les/x/spl les/0.5) HEMT fabricated on a GaAs substrate was studied in detail. The large cutoff frequency f/sub T/ and the effective saturation velocity v/sub s/ for the HEMTs with a large InAs-mole-fraction confirm the effectiveness of using a thick In/sub x/2/Ga/sub 1-x/2/As buffer layer to grow a highly mismatched In/sub x/Ga/sub 1-x/As/AlGaAs HEMT structure on a GaAs substrate. The were obtained at InAs-mole-fraction x of 0.4. The v/sub s/ and the mobility /spl mu/ showed different x dependence. This was explained by considering a different scattering mechanism which dominated the v/sub s/ and the /spl mu/. A 25-30% increase in the v/sub s/ was observed by decreasing the temperature from 300 to 20 K.